Ball End Mill Edge Geometry for Surface Finish and Pick Feed
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Solution Overview
Problem
Conventional ball end mills face challenges in improving machining efficiency when cutting both planar and curved surfaces, as surface roughness tends to decrease with linear cutting edges on curved surfaces.
Innovation Solution
The proposed ball end mill features a ball end cutting edge with large diameter edges formed in an arc shape, having a curvature radius larger than the ball radius, covering 80% to 120% of the ball radius from the center to the outer peripheral end, which enhances surface roughness and allows increased pick feed for improved machining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If linear cutting edges are used to improve machining efficiency on planar surfaces, then surface roughness deteriorates on curved surfaces
Solution Approach 1:
The cutting edge is designed with different local geometries: large diameter edges (with curvature radius larger than ball radius) are positioned at the distal end for planar surface cutting to improve surface roughness, while small diameter edges (with curvature radius smaller than ball radius) are positioned at the outer peripheral end for curved surface cutting to maintain machining efficiency. This local differentiation allows each region to optimize for its specific cutting task.
Solution Approach 2:
The ball end cutting edge is segmented into multiple distinct cutting edges with different curvature radii. The large diameter edges and small diameter edges are separated into different radial zones, allowing independent optimization of cutting parameters for planar and curved surface machining. This segmentation enables the tool to handle both surface types effectively without compromising either surface roughness or machining efficiency.
2Manufacturing precision
If pick feed is decreased to improve surface roughness with arc-shaped ball end cutting edge, then machining efficiency deteriorates
Solution Approach 1:
By providing large diameter edges with curvature radius larger than the ball radius at the distal end, the tool can achieve good surface roughness on planar surfaces with larger pick feeds. The local geometry modification allows increased stepover without sacrificing surface quality, directly resolving the contradiction between surface roughness and machining efficiency.
3Manufacturing precision
If large diameter edges with curvature radius larger than ball radius are used to improve surface roughness, then the ability to cut curved surfaces with small curvature radius deteriorates
Solution Approach 1:
The cutting edge is segmented into large diameter edges for planar surfaces and small diameter edges for curved surfaces. The small diameter edges (with curvature radius smaller than ball radius) positioned at the outer peripheral end maintain the ability to cut curved surfaces with small curvature radii, while the large diameter edges improve surface roughness on planar surfaces. This segmentation preserves versatility across different surface types.
Solution Approach 2:
The solution extends the cutting edge design from a single curvature radius to multiple curvature radii in the radial dimension. By varying the curvature radius of different cutting edges along the radial direction, the tool gains the capability to adapt to both planar and curved surfaces with different curvature requirements, effectively adding a dimensional parameter for versatility.
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(c)
Figure 3
AI summary
Large diameter edges 111a to 111e formed in arc shapes having curvature radii larger than a ball radius R1 are provided. This allows improving surface roughness of a machined surface by cutting of a planar surface with the respective large diameter edges 111a to 111e compared with cutting of a planar surface with a ball end cutting edge formed in an arc shape having a single curvature radius. Further, since the respective large diameter edges 111a to 111e are formed in the arc shape, compared with cutting of a curved surface with linear cutting edges, surface roughness of a machined surface can be improved by cutting a curved surface with the respective large diameter edges 111a to 111e. Accordingly, a pick feed during the cutting of the planar surface and the curved surface with the respective large diameter edges 111a to 111e can be increased, and therefore machining efficiency in the cutting of both of the planar surface and the curved surface can be improved.